1. Field of the Invention
The invention relates to a live-roller feed bed for conveying individual lengths of rolled stock in close succession to cooling beds of a rolling plant.
2. Description of the Prior Art
It is already known to provide live-roller feed beds upstream of cooling beds, for conveying individual lengths of rolled stock in close succession, with a switch or diverter which can be pivoted in a horizontal plane. By means of the switch the individual lengths running in succession in the live-roller feed bed and cut off from a rolled stock billet are each conveyed by their leading end into the fixed longitudinal trough section of a conveying roller table following the discharge end of the switch and comprising two parallel longitudinal troughs, one of which, at the side towards the cooling bed, is in the form of a vertically displaceable braking slide section, and the other of which is in the form of a fixed trough. The two longitudinal sections are separated from one another by a longitudinal section with vertically displaceable separating strips.
When the leading end of an individual length of rolled stock enters the pivotably movable switch section the separating strip is raised in the following trough section, so that the fixed longitudinal trough is separated from the vertically displaceable braking slide section and only after the individual length of rolled stock has run far enough in the fixed trough can it slide over into the longitudinal braking slide section on the conveying plane inclined towards the cooling bed transversely to the conveying direction, after the separating strips have been lowered. Since the separating strips must be raised again before the trailing end leaves the switch, so as to be able to guide the leading end of the following individual length into the fixed trough again, the trailing end of the preceding individual length is withdrawn into the longitudinal braking slide section over the raised separating strip, it being impossible to avoid damage to the surface of the trailing end on account of the upper edge of the separating strip. In addition, at high running speeds of the individual lengths of rolled stock there is a risk of lashing of the trailing end when running over the raised separating strip or entangling the trailing end on the front separating strip.
There is normally no problem in separating the leading trailing end from the following leading end of a rolled stock billet with a round cross-section cut by cross-cutting shears during motion, as long as these lengths of rolled stock with a round cross-section are guided for example in closed tubular guides and are wound up on winders to form rings. Before the leading end of the following individual length of rolled stock is discharged, the switch can be shifted to the new rolled stock guide, so that the trailing end of the leading individual length of rolled stock is withdrawn into the tubular guide in an S-shaped manner and there is no lashing or springing out.
It becomes more difficult if the rolled stock billet must be subdivided into individual lengths upstream of cooling beds of small-section rolling trains. In this connection the rolled stock guides are open towards the top in a U-shaped manner and laterally inclined towards the cooling bed side. In addition, depending on the rolling program, round, flat, angled and U-shaped profiled rods of varying cross-sectional dimensions are conveyed, so that the rolled stock guides must be made relatively wide. Up to approach speeds of approximately 14 m/sec it is possible to separate the successive rolled stock ends from the following leading rod ends by diverting the leading ends without gaps, by tongues raised shortly before the arriving rod ends or wedge-shaped, vertically displaceable plates disposed upstream of the braking slides. In this way the end of the leading length of rolled stock is positively raised, which leads to failure in the case of higher speeds.
Horizontal diversion of the leading end improves the conditions during separation to a certain extent and is possible up to about 16 m/sec. At higher speeds a gap is formed between the end of the separated individual length of rolled stock and the leading end of the following individual length by increasing the conveying speed of the live-roller feed bed with respect to the discharge speed of the rolled stock billet from the rolling train, behind the cross-cutting shears, so that it is possible to change the switch during the gap between the rods without the rod being touched. This can be carried out reliably in operation provided a gap of from 3 to 4 m at a travel velocity of 20 m/sec can be formed. However there are disadvantages. Thus, for example, in the case of an acceleration of the live-roller feed bed of 10% with respect to the rolling speed a distance of 40 m is needed, in order to obtain a gap of 4 m. This necessitates a greater length of the manufacturing shop and additional investment costs. Since braking must be carried out from the increased velocity, there is also an extended braking path. A further disadvantage in the case of roller table rollers driven at increased velocity is that as long as the length of rolled stock is in the rolling train the rollers driven at increased velocity revolve continuously under the length of rolled stock, thus resulting in a high degree of roller wear and in damage to the surface of the material. In the case of relatively small shorts a gap cannot be formed at all, since they follow the leading individual lengths much earlier. Accordingly separation is no longer possible where shorts are very small.